The present invention relates to a developing agent to be employed in an image-forming apparatus such as an electrophotographic device, an electrostatic recording device.
The toner to be employed as a developing agent is generally consisted of raw materials including a binder resin, a coloring agent, a wax and a charge control agent. These raw materials are dispersed and kneaded at first, and then pulverized so as to obtain toner particles having a predetermined size. The toner particles are then surface-treated so as to allow an additive such as silica to adhere onto their surfaces, thereby obtaining the toner. This toner can be singly employed as a one-component developing agent or may be mixed with a carrier so as to be employed as a two-component developing agent.
In recent years, it has become possible, on the occasion of forming an image, to perform the development of image in various modes including not only single color or full color modes but also photography finish mode or sepia color mode.
At present, if an image is to be formed with a single color mode, carbon black is mainly employed as a coloring agent for a black developing agent to be employed in this case. There is a problem however that the carcinogenicity of carbon black has been altered in rank from Class 3 to Class 2B on Apr. 12, 1996 by the IARC (International Agency for Research on Cancer). This Class 3 is equivalent to say that it is still insufficient to determine whether the substance is carcinogenic or not. On the other hand, the Class 2B is equivalent to say that the substance is already recognized of its carcinogenicity as far as animals excluding human body are concerned, and there is also a possibility of carcinogenicity of the substance with respect to human body. Therefore, there is an increasing demand for a more safe black coloring agent which is capable of substituting for the carbon black.
There are known two kinds of electrophotographic developing method which are useful for forming an image in a sepia color mode. One of the methods is a full color developing system wherein four kinds of toner, i.e. yellow, Magenta, cyan and black, are superimposed so as to reproduce an image with sepia color. The other is a monochromatic developing system wherein a black toner is employed so as to reproduce an image with halftone.
However, in the former system, a mottled appearance is more likely to be generated due to the misregistration of colors. On the other hand, in the latter system, since the hue inherent to carbon black differs apparently form the hue of sepia color, color drift would be caused to occur. As explained above, it has been very difficult according to the prior art to reproduce an image in a sepia color mode, which is excellent in uniformity and also in color reproducibility.
Therefore, an object of this invention is to provide a developing agent which makes it possible to obtain an image which is excellent in uniformity and also in color reproducibility without necessitating the employment of carbon black which may be harmful to human body.
Another object of the present invention is to provide an image-forming apparatus which makes it possible to obtain an image which is excellent in uniformity and also in color reproducibility without necessitating the employment of carbon black which may be harmful to human body.
According to the present invention, there is provided a developing agent comprising a sepiomelanine pigment as a coloring agent, and a binder resin.
According to the present invention, there is also provided an image-forming apparatus comprising;
an image carrier;
a developing device for forming a developing agent image through a development of an electrostatic latent image formed on the image carrier, the developing device being disposed to face the image carrier and designed to accommodate a developing agent comprising a toner containing a sepiomelanine pigment as a coloring agent, and a binder resin;
a transferring device for transferring the developing agent image onto a recording material; and
a fixing device for fixing the developing agent image transferred onto the recording material.
According to the present invention, since a sepiomelanine pigment can be employed singly as a coloring agent, it is now possible to obtain an image which is excellent in uniformity and also in color reproducibility. Further, since a sepiomelanine pigment which is a natural organic pigment is employed as a coloring agent, it is possible to form a brown or black image without necessitating the employment of carbon black whose carcinogenicity is worried about at present.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.